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J

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Discussion Starter #1
The last day I was studing the "VvTI" system of a BMW 328i .
Its very simple and use a rubber piece to adjust it with the revolutions speed....
I am thinking to the possibility of use my AEM cam gears to try it.
with the help of a stroboscope light and some different rubber thickness.....and of course the help of a DYNO (this is my problem)
The BMW unit use a five bolt , mine have three but if will be necessary I can buy a set of five bolt cam gears....

some one want to help??

My first idea when I bought My car was to put a switch in a AT gearbox (but if the AT only an hold 400 HP...) and now you can put it in your AT gearbox.....way not it will be an Upgrade for our cars.?
 

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2/3 HP to the Paws
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VVT-i is largely an emissions bandaid, which does help torque production in very small engines by a tiny margin.

You don't need, or want it on a 7m.
 

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Dr. Jeff Lange
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Supra_Dre said:
im sure it'll do more good than bad even if its a small margin.....the 2jz is a similar engine and later models came with VVTi
I always heard that the non-VVT-i ones were much easier to put out the power with, because you don't always have to deal with VVT-i. (Only the Japan models after 98 got VVT-i on the TT, and 98 was the only model any Supra came with VVT-i in North America, and it was on the N/A)

I don't think it's worth it.
 

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2/3 HP to the Paws
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Supra_Dre said:
im sure it'll do more good than bad even if its a small margin.....the 2jz is a similar engine and later models came with VVTi
Not if you're concerned with performance, it won't. VVTi effectively robs the engine of low rpm power by advancing the intake cam in an effort to improve emissions and fuel economy.

That doesn't stop the marketing drones from hyping it as a performance system, however, much like vtec. In reality, however, it's more an emissions system than anything else.

There are power gains to be had with variable valve timing, but for them to be worthwhile, you need to tune both cams, and the timing needs to be optimized for performance rather than emissions and economy.

Suffice it to say, doing this would not be cheap, and similar results can be realized by simply adding a few pounds of boost.
 
J

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Discussion Starter #8 (Edited)
Enraged said:
hey josbeat, do you have your custom intake manifold on the car yet? is it running? pics?
Yes it´s running great! mmmm not I will say very very great!
If you need help.....
the Pics:
http://es.f1.pg.photos.yahoo.com/ph/josegpy/lst?.dir=/Intake+Manifold&.view=t

and here in the engine Bay:
http://es.f1.pg.photos.yahoo.com/ph/josegpy/lst?&.dir=/engine&.src=ph&.begin=9999&.view=t&.order=&.done=http://es.f1.pg.photos.yahoo.com/ph/josegpy/lst?&.dir=/engine&.src=ph&.view=t


SIMBA-
all I know is you are great technician , I respect you a lot.
But I was thinking that the VVTi or VTEC.... you know the variable timing of the cams was to get a best torque band possible.....of course better torque band bettert fuel milenage....

and in my self probs with the AEM cam gears I found that when I move those to + or- I feel the engine have different power bands.....
you don´t think if we can get better low end and better top end at the same boost.... is good?
 
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Discussion Starter #10
josbeat

i dont understand how you think your going to move the cams during rotaion?

and on your TB how did you get the cable to go backwards instead of in front of the TB(like stock)?
 
J

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Discussion Starter #11
GreaseMonkey said:
josbeat

i dont understand how you think your going to move the cams during rotaion?

and on your TB how did you get the cable to go backwards instead of in front of the TB(like stock)?
1° copying the BMW system they are using a rubber piece between the first wheel ( atached to the cam in the center) and the other wheel ( in contact with the belt) using any type of ajustable cam gear.....
the rubber piece is elastic so wheen the rev. go up the rubber retard the cam to open the valves.
I hope you understand my.

2° loose the nuts of the cable linkage to the throtle
cut the side of the cruise controler and turn it .... the throtle are turned also....
Tell my if u can see that big picture.

http://es.f1.pg.photos.yahoo.com/ph/josegpy/vwp?.dir=/engine&.dnm=Im000478---1.jpg&.src=ph&.view=t&.hires=t
 
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BMW's vvti is much more complicated than you're explaining it. It essentially uses a movable rocker arm to adjust lift and duration. The whole idea of vvti is to have infinite adjustability (within spec of the cams and adjustability of teh rocker point) whereas systems like vtec just switch between two sets cam lobes. It is a computer controlled system that adjusts to throttle input, rmp and load.

In other words, you'll never get it on a 7m and if you did, you wouldnt be able to tune it. BMW has a lot more $ and resources than you do.
 

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2/3 HP to the Paws
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josbeat said:
But I was thinking that the VVTi or VTEC.... you know the variable timing of the cams was to get a best torque band possible.....of course better torque band bettert fuel milenage....
The problem is in the tradeoff each system makes to achieve its design goals.

VTEC and VVT-i control the intake cam timing and/or profile with the primary goal of lowering emissions. In addition to doing this, some very small engines (e.g. 2L and under) can see a tiny increase in torque as a result of changing the profile and/or timing of the intake cam at low rpm.

The tradeoff is a significant loss in power at lower RPM due to the geared-towards-emissions-and-economy cam profiles that virtually every variable cam timing system uses at low RPM.

While there is a slight increase in torque on smaller engines, there is a dramatic loss of overall power at lower rpm. This is not good. A standard cam ground and timed to specs designed to increase performance will improve torque and power at low, mid, and high rpms. (There are tradeoffs, of course, depending on the grind)

The concept of Variable Valve Timing can be applied to make power. E.g. you can use "normal" hot cams as the low-rpm profile with a given timing, then switch to the "hot" cams at higher rpm to increase flow. However, virtually no consumer VVT system does this. Instead, they have a "normal" cam which is activated at high RPM's, and an "economy" cam used for low RPM's.

So, yes, if you were wanting to build the street application from hell and effectively build your own VVT system, you could see some benefits to such a system assuming it was tuned for overall performance. However, you can just as easily make that extra power by playing with the overall ignition timing advance under the boost curve, while leaving the cams where they are.

In the context of this, VVT systems are useless on torquey turbocharged engines such as the 7m and 2jz. If you want economy, buy a honda. If you want performance, there are significantly cheaper and more effective options (read: Boost) to create it.

Assuming a perfectly developed and tuned VVT system, you may see a benefit of 20-30 pounds of torque and perhaps the same again in horsepower production in various areas on the power curve.

Add two pounds of boost and you get the same thing on the entire curve.

You can blow ten grand building up a 7m with a bigass turbo and fuel system, and go out and make 700 odd horsepower, or you can blow ten grand building a VVT system and get another 20 or 30 horsepower out of it along with slightly better fuel mileage and emissions.

Which makes more sense to you?
 

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wastegate hose is pulled
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Eh... The BMW "VANOS" system is not a VTEC variable lift system like a Honda uses.

It is desireable on ANY engine. Regardless of size or induction method adjusting camshaft timing optomizes cylinder filling for diferent RPM ranges. It is just too bad that there is no simple piece of rubber that is going to do that. Here is how the BMW system actually works- http://www.bmwworld.com/technology/vanos.htm It is a complex computer controlled system only available to OEM level manufacturers. In other words it is a pipe dream. :(
 
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Discussion Starter #15
simba hit it on the head with his last paragraph. its funny with all these newbies trying to come up with these crazy new technologys they "can" do, when its obviously not used on the 700-1000 hp supras that exist on this forum
 
J

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Discussion Starter #18 (Edited)
sorry
I only want to make the "SF" more interesting...
Sorry but all BMW have not a vvti electronic controled.
Pics soon, give my one day more to take pics from a book and directly to the BMW engine.
and if you seek in the web you will found some electric systems to put in some cars to adjust the timing cam ...yes electric with little electric motors and controller.

Is an idea only!!!!
I am not a newbies ,I was working with engines from six yeard old and now I have 34 , but I like to invent things you know! to keep my head working.
 
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Discussion Starter #19
And yes we are not talking about the lobe heigh ,talking about to move the Cams...
 

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Moderator, megalos ntabatzis!!
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i can see what youre all saying, what i dont see is how you would think this would yeild no results? wouldnt it improve the entire powerband, its like being able to run low lift smaller duration cams untill boost hits then you get bigger lift/duration, essestially, youll make more power down low and up top on stock head... Or am i misunderstanding this concept?

Obviously the advantage is not worht the money required, as simba said 2 psi would yeild the same power, but would it yeild the same overall driveability? probably not.

Unfortunetly we have yet to see a tuned vvt-i engine with some sort of upgraded cams due to the fact that the tech. is rare in supras in north america. Im sure its not as bad as you guys are making it out to be...
 
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